1. Field of the Invention
The invention relates to a pressure plate assembly, especially for a friction clutch.
2. Description of the Related Art
Various embodiments of these types of pressure plate assemblies are known from U.S. Pat. No. 6,409,002. In the known multi-disk pressure plate assemblies, an intermediate plate and the pressure plate of the plate arrangement are separated from each other during a clutch-release operation by a helical compression spring acting between them; the intermediate plate and a flywheel acting as an abutment are also separated from each other by a similar spring. So that the pressure plate and the intermediate plate can be connected for rotation in common to the clutch housing, which is designed as an integral part of the flywheel, these components are designed with radially outward-extending projections for rotational engagement, which fit into rotational-engagement openings in the housing. Restoring force-generating elements, which act between the pressure plate and the intermediate plate on one side and the housing on the other side, are provided to pretension the plates in the circumferential direction into a centered position in which the rotational-engagement projections assume an essentially central position within the associated rotational-engagement openings. In this centered position, there is essentially no contact between the rotational-engagement projections and the housing. As a result, the rotational-engagement projections will not interfere with the release of the clutch even if they have dug slightly into the material of the housing.
It has been found that the use of shaped springs as restoring force-generating elements to center the intermediate plate and the pressure plate in the housing and also the use of compression springs to control the separation between the flywheel and the intermediate plate and between the intermediate plate and the pressure plate are not optimal, because the functions they serve are affected by the rotational speed of the components. In addition, the known designs are relatively complicated and thus are also expensive to manufacture.
A need, therefore, exists for a pressure plate assembly provided with separation control performed by the releasing spring arrangement and/or the positioning of the plate arrangement in the housing which is affected less strongly by centrifugal force and is less dependent on rotational speed.
Still another need exists for a pressure plate assembly that has a simple mechanical design and thus can be produced at low cost.